Computer systems are comprised of a set of components that communicate with each other over buses and similar communication lines. Computer system components include processors, communication chipsets, memory modules, peripheral components and similar devices. These devices communicate with one another over a set of buses. These busses may utilize communication protocols understood by each of the components on the bus. Some components act as bus controllers to manage communication traffic on the bus.
Computer system speed and efficiency is limited by the speed of buses and communication lines in the computer system. A processor relies on a system bus, memory bus and memory controller for retrieving data and instructions from system memory. The processor is limited in the speed at which it can process these instructions by the speed at which it can receive the data and instructions over the system bus and memory bus from system memory.
Buses are typically communication lines laid out on a printed circuit board such as the main board of a computer system. Components in the computer system have pins that connect to the lines of the bus. The components communicate across the bus by driving a signal across lines of the bus. These signals are latched by a recipient device. The signal is terminated by an on board termination circuit which includes a resistor or similar component. If a signal is not properly terminated then a reflection of the signal may occur or other noise may affect subsequent signaling on the line.